Al Horford, playing another strong all-around game, fought off second-half foul trouble and finished with 20 points, nine rebounds and eight assists for Boston (21-4).
Rookie Jayson Tatum scored 14 of his 17 in the first quarter, and Aron Baynes had 10 points in the win. Boston's Jaylen Brown got in early foul trouble but finished with eight points and seven rebounds in 22:58.
Horford was a plus-21 in 34:40. He picked up his fourth foul with 7:32 left in the third quarter and never did get a fifth.
Irving, who shot 13-for-24 from the floor, had 19 points in the second half, including five in a row with his team up seven with 90 seconds remaining. He also contributed four rebounds and a pair of steals.
The Celtics, who took the lead for good at 7-6 and led by as many as 20 points, improved to 3-1 on their current five-game homestand. They have won 11 of their last 12 at home and 21 of their last 23 games overall.
Boston ran up a whopping 45-28 rebounding advantage.
Antetokounmpo, delivering his third straight 30-point game, was 14-for-24 from the floor and 12-for-14 from the foul line. He also had nine rebounds, four assists and four turnovers. Most of his baskets came driving to the basket, his outside shot a struggle.
Khris Middleton scored 19 points, Eric Bledsoe 18, Tony Snell 11 and Malcolm Brogdon 10 in the loss.
The Bucks fought back from a 20-point third-quarter deficit to get with seven. They could get no closer as the Celtics won the season series 2-1.
Milwaukee (12-10) lost for the second time in its past seven games.
NOTES: The Celtics were the first team in the NBA to reach 20 wins, accomplishing the feat for the 15th time in their storied history. They reached the NBA Finals in 13 of the previous 14. ... It was Greek Heritage Night at TD Garden, fitting with F Giannis Antetokounmpo, the Greek Freak, in town. He received a huge ovation in pregame introductions. ... The Bucks play at Detroit and the Celtics host the Dallas Mavericks on Wednesday night.